Impulse contral data (motoric inhibition) and personality data (Freiburger Persönlichkeitsinventar = a self-report inventory) were used in an experiment in which the subjects were 240 males in late adolescence, delinquents in prison (n = 90), released delinquents (n = 30), army recruits (n = 90) and factory workers (n = 30). These groups, matched with regard to age and social class, were selected in order to identify possible effects of delinquency as well as of an institutional environment. It was found out that the delinquency factor was the only one having an effect. In the case of delinquents, as compared to non-delinquents, less (behavioural) impulse control, stronger "extraversion" tendencies, more nervousness, aggressiveness, depression, excitability, openness and emotional instability could be observed. Implications of the "impulse control" variable with a view to rehabilitation work are mentioned.